The present invention relates to an AC-type plasma display apparatus (PDP apparatus) used as a display unit of a personal computer or work station, a flat TV, or a plasma display for displaying advertisements, information, etc.
In an AC-type color PDP apparatus, an address/display separation system is widely adopted, in which a period for selecting cells to be used for display (address period) and a display period (sustain period) for causing a discharge to occur to light cells for display are separated. In this system, charges are accumulated in the cells to be lit during the address period and a discharge is caused to occur for display during the sustain period by utilizing the charges.
PDP apparatuses include: a two-electrode type apparatus in which a plurality of first electrodes extending in a first direction are provided in parallel to each other and a plurality of second electrodes extending in a second direction perpendicular to the first direction are provided in parallel to each other; and a three-electrode type apparatus in which a plurality of first electrodes and a plurality of second electrodes each extending in a first direction are provided, by turns, in parallel to each other and a plurality of third electrodes extending in a second direction perpendicular to the first direction are provided in parallel to each other. Recently, the three-electrode type PDP has become widely used. Moreover, a structure having more than three kinds of electrodes, including electrodes that play an auxiliary role, has been devised.
In a general structure of the three-electrode type PDP, first (X) electrodes and second (Y) electrodes are provided by turns in parallel to each other on a first substrate, third (address) electrodes extending in the direction perpendicular to the first and second electrodes are provided on a second substrate facing the first substrate, and each surface of the electrodes is covered with a dielectric layer. On the second substrate, one-directional stripe-shaped partitions extending in parallel to the third electrode are further provided between the third electrodes, or two-dimensional grid-shaped partitions arranged in parallel to the third electrodes and the first and second electrodes are provided so that the cells are separated from one another and after phosphor layers are formed between the partitions, the first and second substrates are bonded together to each other. Therefore, there may be a case where the dielectric layers and the phosphor layers and, further, the partitions, are formed on the third electrode.
After the charges (wall charges) in the vicinity of the electrode in each cell are brought into a uniform state by applying a voltage between the first and second electrodes and addressing is performed to selectively leave the wall charges in a cell to be lit by occurring discharges between the first, second and third electrodes by applying a scan pulse sequentially to the second electrode and applying an address pulse to the third electrode in synchronization with the scan pulse, a sustain discharge is caused to occur in the cell to be lit, in which the wall charges are left by the addressing, by applying a sustain discharge pulse that makes the neighboring electrodes, between which a discharge is to be caused to occur, have opposite polarities by turns. The phosphor layer emits light, which is seen through the first substrate, by the ultraviolet rays generated by the discharge. Because of this, the first and second electrodes are composed of an opaque bus electrode made of metal material and a transparent electrode such as an ITO film, and light generated in the phosphor layer can be seen through the transparent electrode. As the structure and operations of a general PDP apparatus are widely known, a detailed explanation will not be given here.
When a discharge gas is enclosed in a discharge space and a discharge is caused to occur between two electrodes, for example, in a PDP, it is known that the threshold voltage (the discharge start voltage) is determined based on the product of a distance d between two electrodes and a pressure p of the discharge gas, and a curve plotted as a graph to represent the change, where the horizontal axis denotes the product and the vertical axis denotes the discharge start voltage, is called the Paschen curve. In the Paschen curve, the discharge voltage reaches the minimum value for a certain value of the product (pd) of the distance d between two electrodes and the pressure p of the discharge gas and such a state is called the Paschen minimum.
In the configuration of the above-mentioned three-electrode type PDP, the transparent electrode of the first and second electrodes has, in general, a shape such that the edges of the electrodes are parallel and face each other at a distance d in each cell. The discharge voltage is obtained from the Paschen curve defined by the distance d and the pressure p of the discharge gas in the discharge space and the discharge start voltage between the first and second electrodes is determined. In this case, the discharge start voltage, determined based on the product pd, differs from cell to cell because there are variations in the distance d caused during the manufacture even if the designed value of the product pd in each cell is the same. As for the drive voltage in an actual PDP apparatus, therefore, the variations in the discharge start voltage being taken into account, the discharge start voltage is set higher than the Paschen minimum so that a discharge is caused to occur without fail even if there are variations in the discharge start voltage.
In Japanese Unexamined Patent Publication (Kokai) No. 2001-84907, for example, it is described that the product pd is set greater than the Paschen minimum in a three-electrode type PDP.
In a three-electrode type PDP, the space (called the reverse slit) between a pair of the first and second electrodes between which a discharge is caused to occur and its neighboring pair is set wide enough in order to prevent a discharge from occurring, but in Japanese Unexamined Patent Publication (Kokai) No. 2001-84906, a configuration is proposed in which a discharge is prevented from occurring in the inverse slit by narrowing the space so that the product pd becomes smaller than a value at which the Paschen minimum is reached and the discharge start voltage is increased.
Further, in Japanese Unexamined Patent Publication (Kokai) No. 2001-52623, it is described that the distance between the transparent electrodes of the first and second electrodes is set to a value at which the product pd is the Paschen minimum in a three-electrode type PDP.
As described above, the publicly known examples describe the distance between the third discharge electrodes in a three-electrode type PDP in which the first and second electrodes are provided by turns on the first substrate and the third electrodes are provided on the second substrate so as to intersect the first and second electrodes, but other PDPS having various configurations have been proposed. Japanese Unexamined Patent Publication (Kokai) No. 2003-36052, for example, describes a PDP which comprises: a first substrate, on which a plurality of first electrodes extending in a first direction are provided in parallel to each other, and after a dielectric layer is provided thereon, a plurality of second electrodes extending in a second direction perpendicular to the first direction are provided in parallel to each other, and a dielectric layer is further provided thereon; and a second substrate, on which a plurality of third electrodes extending in the first direction are provided in parallel to each other so as to face the first electrodes, and a dielectric layer is provided thereon. In this configuration, the first and second electrodes at which a discharge is caused to occur are configured so as to intersect each other via the dielectric layer, and the distance between two electrodes at the intersection is zero and the distance between two electrodes increases gradually as the distance from the intersection increases. Because of this, there must be a point at which the Paschen minimum is reached.
Moreover, Japanese Unexamined Patent Publication (Kokai) No. 2001-283735, describes a two-electrode type PDP which comprises: a first substrate, on which a plurality of first bus electrodes extending in a first direction are provided in parallel to each other and after a dielectric layer is provided thereon, a plurality of second bus electrodes extending in a second direction perpendicular to the first direction are provided in parallel to each other and a dielectric layer is provided thereon; and a second substrate having partitions and phosphor layers. At the intersection of the first and second bus electrodes, first and second transparent electrodes to be connected to the first and second bus electrodes, respectively, are provided and the first and second transparent electrodes have edges facing each other at a constant distance d. In Japanese Unexamined Patent Publication (Kokai) No. 2001-283735, the distance d between the first and second transparent electrodes is not described particularly, and there is no description of the Paschen curve and the Paschen minimum.